Flow-controlling apparatus



March 1 1927. 1,619,253

I G. H. GIBSON FLOW CONTROLLI NG APPARATUS Original Filed June 3. 1920 f INVENTOR ATTORNEY Patented Mar. 1, 1927.

UNITED STATES PATENT OFFICE.

FLOW-CONTROLLING APPARATUS.

Original application filed June 3, 1920, Serial No. 349.303. Divided and this application filed August 10,

1923. Serial No. 656,765.

My present invention comprises improvements in apparatus for controlling fluid rates of flow, and was primarily devised, and is. especially adapted for use in maintaining a predetermined ratio between the rate at which steam is withdrawn from a boiler and the rate at which air is supplied to the boiler furnace to support com bustion therein.

The present invention consists essentially in improvements on apparatus heretofore devised by me, and the primary purpose of the present improvements is to provide for compensatory adjustments in response to to such a variation in the physical condition of one of the flowing fluids as a. change in the pressure of the steam or a change in the density of the air.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and, forming a part of this specification.-

For a better understanding of the invention, however, its advantages and specific objects attained with its use, reference should be had to the accompanying drawings and descriptive matter in which I have illustrated and described a preferred embodiment of the invention.

The one figure of the drawing is a diagrammatic representation of apparatus for automatically measuring and maintaining a predetermined ratio between two fluid rates of flow. In the drawing, A represents a conduit through which one fluid flows, and B represents another conduit-through which a second fluid flows, at a rate which depends upon the rate of flow through the conduit A. The conduit A may be the steam outlet pipe from a boiler, and the conduit B may supply air to the boiler furnace to support the combustion therein. Associated with the conduit A is an electromagnetic flow balance C, the purpose and effect of which is to maintain an electric control currentproportional in strength to the rate of steam flow through conduit A. As shown, the balance C com rises a lever C, pivoted at C and having t ree arms. One of these arms is horizontal and carries an adjustable counterweight C". A, second arm is vertical and carries an electric coil C. The third arm is horizontaland opposed to the first mentioned arm and is connected to the diaphragm D of a differential pressure device D. The latter comprises a chamber divided into two compartments by the diaphragm D. The diaphragm D is subjected to a diflerential pressure which is a function of the rate of flow through the conduit A, and this differential tends to tilt the lever C in the clock-wise direction, whereas the counterweight C tends to tilt the lever in the opposite direction. The means shown for impressing the desired differential pressure eifect on the diaphragm D comprises a restricted orifice A in the conduit A, a pipe a, connecting the pipe A at the supply side of the orifice A to the compartment of the device D above the diaphragm D, and a pipe a connecting the pipe A at the discharge side of the orifice A to the compartment of the device D below the diaphragm D.

- The coil C carriedby the lever C forms, in effect, the floating coil of a Kelvin balance, havingtwo stationary coils C The coils C and C are connected in series and an electric current is maintained t erethrough of the proper intensity to normally maintain the lever C in its neutral position notwithstanding fluctuations in the difl'erential pressure acting on the diaphragm D. The means shown for this purpose comprise a source of electric energy as supply conductors 1 and 2 between which the coils O and O are connected in series with a rheostat E, and the coils G and C of a flow balance CA hereinafter referred to. The rheostat E is adjusted by a reversible electric motor F, having three terminals,

one of which is connected to the supply conducto'r 1, while the other two are connected to switches G and G, respectively, by conductors? and 8 respectively. The switches G and G are also connected by a common conductor 9 to the supply conductor 2.

When the differential pressure on the diaphragm D increases and the lever C tilts in the clock-wise digection, it closes the normally open switch G and causes the motor F to turn in the direction required to adjust the rheostat E so as to decrease the resistance in series with the coils C and C of the balance 0, and thereby increase the current through saidcdils and restore the lever to its neutral position imwhfih the switches G and G. are both open. On a decrease in the difierential pressure acting on the diaphragm D and a consequent tilting of the lever C in the counter clock-wise direction, the switch G is closed and the motor F then turns in the direction required to adjust the rheostat E so as to increase the resistance in series with the coils C and C of the balance 'C and thereby reduce the current through said coils and thus restore the balance lever G'to' its neutral position.

The balance CA is similar in character to the balance C, and is acted upon by a difierential pressure mechanism DA responsive to the rate of fluid flow through the conduit B. The differential pressure mechanism of the balance CA, as shown, com rises bells (Z and (1', connected to the opposite horizoncoils of the two balances, and 5 the conductor connecting the coils of the balance CA to the supply conductor 2. The balance GA, throu switches G and G controls a. re-

versib e motor FA just as the balance C con-- trols the motor F as shown. One terminal of the motor FA is connected to the supply conductor 1, by a conductor 60, and the other two terminals of the motor FA are connected by conductors and to the switches G and G respectively, of the balance CA, these switches G and G being also connected to the supply conductor 2 by a conductor 90.

The motor FA operates a dam r 7 controlling flow through the conduit B. As shown, the motor FA is provided with a threaded spindle F in engagement with a nut carried by the dam er, so that when the motor rotates in one irection the damper is adjusted in the closing direction, and when the motion of the motor is reversed, the damper is opened. The motor FA and the balance CA are arranged to cause the damper to close and throttle the flow through the conduit B when the lever C of the balance CA tilts in the clock-wise direction, and on a reverse movement of the lever, the damper is opened thus increasing the flow through the conduit B.

The operation of the apparatus so far described tends to maintain a fluid rate of flow through conduit B, which is proportional to the fluid rate of flow through conduit A, in accordance with the invention disclosed and claimed by me in'my co-pending applicaion, Serial No. 121,547, filed Sept. 22, 1916, and patented May 5,1925, Pat. No. 1,537,044. This mode of operation may be explained as diaphragm H has its stem follows: The pressure difierential acting the balance CA normall maintains a flow through the conduit proportional in strength to the electric current flowing through the coils of both balances, the flow through the conduit 13 is thus maintained pro ortional to the flow through conduit A.

T e supply of air supporting combustion to the boller furnace in constant proportion to the rate at which steam is withdrawn from the boiler, tends to maintain a constant steam pressure, but in practice it is ordinarily impossible to avoid some fluctuations in steam pressure and in accordance with the present invention 1' provide means for increasing and decreasing the air flow throu 11 the conduit 13, relative to the steam flow t lrough conduit A, as the steam pressure decreases and increases. Forthis purpose I connect a resistance K in a shunt about the windings C and C of the balance CA and adjust the amount of resistance K in this shunt, accordingly, as the static pressure in the conduit A falls below or rises above a predetermined value. To thus vary the amount of the resistance K in the shunt circuit, I employ a fluid pressure motor H having a diaphragm H subjected at one side to the static pressure in the conduit A which is transmitted to the motor H by the pipe a, and subjected at the other side to the opposing action of a s ring H. The 3 connected to a pivoted switch arm I. As the static pressure in the conduit A decreases, the arm I is adjusted to increase the amount of the resistance K in the shunt circuit. The eifect of the shunt includin the resistance K varied as above descri ed, in response to variations in the static pressure in the conduit A, is to vary the ratio between the fluid rates of flow in the conduits A and B as the static pressure in the conduit A varies, so as to diminish or increase the supply of air to the boiler furnace as the steam pressure in the boiler rises above or falls below a predetermined normal pressure.

To automatically-compensate for variations between the rateof flow through the conduit 13 and the resultant differential between the pressure transmitted to the balance CA w iich are produced by change's'in air density resulting from changes intem- .perature of the air passing through the conduit B, a suitable resistance R is located in the conduit B, and is connected in shunt to the coils C and G of the balanceGA;

The efiect of a rise in temperature in the air passing through .the conduit Bfis to decrease the density of the air. A consequence of this density change is, that for a given differentlal of pressure impressed on the fluid pressure motor bell d and d, the weight rate of flow will be decreased by a decrease in the air density. The shunt resistance R, if of such material that its electrical resistance will increase with the temperature of the air to which it is exposed, compensates more or less for the change of air density by diverting more of the balancing current away from the coils (J and C of the balance CA when the air is relatively 0001, than when it is relatively hot. 'By choosing for the resistance body R, a material the resistance of which changes with its temperature at the proper rate, and by properly proportioning this resistance with respect to the resistance of coils C and C the compensation thus obtained may be made almost mathematically exact for ordinary ranges of temperature variations. The principles by which the material for said resistance body R is chosen and this resistance is proportioned with respect'to the coils C and C are fully explained in my co-pending application Serial #247.858, filed August 1,

1918, and patented Feb. 10, 1925, Pat. No.

1,525,807. It is suflicient to say herein that thedesired result will be obtained in the 1present case, if the air density is expressed y the equation d: ,/1 +Bt I wherein (Z is the density at the temperature t, and C and B are constants, and if the resistance at any temperature t, of the resistance body R is expressed by the equation R=Ro(1+Dt), wherein R represents the resistance at any temperature If, and R0 and D Y are constants. With these assumptions, the desired compensation will be obtained when R0 is small with respect to the resistance of coils C and C and B is twice as large as D. M and M are ammeters showing the electric currents flowing through the 00115 or the balances C and CA respectively.

of embodiment of my invention now known to me, it will be apparent to those skilled in the art that changes may be made, in addition to those specifically suggested above.

without departing 'from the spirit of my invention asflset forth, in the appended claims, and that certain features of myinvention may be used to advantage in such cases without a corresponding use of other features.

Having now described my invention, what I claim as new and desire to secure by Letters Patent, is:

'1. In apparatus for maintaining a definite ratio between the strength of an electric current and a fluid rate of flow, the combination with a differential pressure motor ac tuated by the flowing fluid, of an electro dynamic motor actuated by said current and opposing the action of the first mentioned motor, and means responsive to a physical condition of the fluid flowing for modifying the said ratio. 2. In apparatus for maintaining a definite ratio between the strength of an electric current and a fluid rate of flow, the combination with a differential pressure motor actuated by the flowing fluid, of an electrodynamic motor actuated by said current and opposing the action of the first mentioned motor. and means responsive to a physical condition of the fluid flowing for modifying the force exerted by said electro-dynamic motor.

3. In apparatus for maintaining a definite- -motor, and means responsive to changes in a physical condition of the fluid flowing for diverting more or less of said current through a shunt about said electro-dynamic motor. a

4. Means for automatically proportioning the rate of flow of one fluid stream to another comprising in combination, a balancing device for each stream including a fluid pressure motor responsive to the rate of flow of the corresponding stream and an opposing electro-magnetic motor, means for connecting the two electro-magnetic motors in series in the same energizing circuit, means actuated by each balance for regulating the ratio between the rate of flow ofthe stream to which the balance pertains and the strength of the electric current passing through the electric motor of the balance, and means for compensating for a change in the density of the fluid flowing through one of said conduits, consequent upon changes in the fluid temperature comprising a shunt about one of said electro-magnetic motors including a resistance having a posltivetemperature c'd-eflicient and subjected to the temperature of said fluid.

5. Means for automatically proportioning the rate of flow of one fluid stream to another comprising in combination, a balancing device for each stream including a fluid pressure motor responsive to the rate of flow of the corresponding stream and an opposing electro-magnetic motor, means connecting the two electro-magnetic motors in series in the same energizing circuit, current re ulating means actuated by one of said bfiances for adjusting the current in said circuit as required to maintain a predetermined ratio between the strength of said current and the rate of flow of the stream to which that balance pertains, means actuated by the second balance for varying the rate of flow of the stream to which the last mentioned balance pertains to thereby maintain a predetermined ratio between that rate of fiow and the strength of said current,

a shunt about the electro-magnetic motor ing device for each stream including a fluid pressure stream and an opposing electroemmas magnetic motor, means connecting the two electro-magnetic motors in series in the same energizin circuit, current regulating means actuated Eymne of said balances for adjusting the current in said circuit, as required to maintain a predetermined ratio between the strength of said current and theirate of flow of the stream to which that balance pertains, means actuated by the second balance for varying the rate of flow of the stream to which the last mentioned balance pertains to thereby maintain a predetermined ratio between that rate of flow and the strength of said current, a shunt about one of: said electro-magnetic motors including a variable resistance and means responsive to the static pressure of one of said streams for adjusting said resistance. v

7 In apparatus for maintainin a definite ratio between the strength of an e ectric current and a fluid rate of flow, the combination with a differential ressure motor actuated by the flowing fiui of an electro-dynamic motor actuated by said current and opposin the action of the first mentioned motor, and means responsive to a physical condition of the fluid flowing for modifying the action of one of said motors upon the other.

Signed at Philadelphia in the county of Philadelphia and State of Pennsylvania this seventh day of August, A. D. 1923.

GEORGE 1-1. GIBSON. 

